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If the first, second and the last terms of an A.P. are a,b,c respectively, then the sum of the A.P. isA. `((a+b)(a+c-2b))/(2(b-a))`B. `((b+c)(a+b-2c))/(2(b-a))`C. `((a+c)(b+c-2a))/(2(b-a))`D. none of these |
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Answer» Correct Answer - C Let there be n terms in the A.P. Then, `c=a+(n-1)(b-a)" "[becaused=b-a]` `rArrn=(b+c-2a)/(b-a)` `:." Sum of n terms"=(n)/(2)(a+c)=((b+c-2a)(a+c))/(2(b-a))` |
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